Delphi語言學習4-函數和方法

//格式
functionfunctionName(parameterList):returnType;directives;
　localDeclarations;
begin
　statements
end;
//例1
functionWF:Integer;
begin
　WF:=17;
end;
//例2
functionWF:Integer;
begin
　Result:=17;
end;
//例3function MyFunction: Integer;
begin
　MyFunction := 5;
　Result := Result * 2;
　MyFunction := Result + 1;
end;

　　2.調用方式

　　Delphi的函數有幾種調用方式，

　　 Directive  Parameter order  Clean-up  Passes parameters in registers? 
register  Left-to-right  Routine  Yes 
pascal  Left-to-right  Routine  No 
cdecl  Right-to-left  Caller  No 
stdcall  Right-to-left  Routine  No 
safecall  Right-to-left  Routine  No 
　例如：

functionMyFunction(X,Y:Real):Real;cdecl;

　　3.函數聲明
//先聲明後實現
functionCalculate(X,Y:Integer):Real;forward;
functionCalculate;
　……{declarations}
begin
　……{statementblock}
end;
//擴展聲明
//1
functionprintf(Format:PChar):Integer;cdecl;varargs;
//2LinkingtoObjectFiles
{$LBLOCK.OBJ}
procedureMoveWord(varSource,Dest;Count:Integer);external;
procedureFillWord(varDest;Data:Integer;Count:Integer);external;
//3ImportingFunctionsfromLibrarIEs
functionSomeFunction(S:string):string;external'strlib.dll';
//Thefollowingdeclarationimportsafunctionfromuser32.dll(partoftheWin32API).
functionMessageBox(HWnd:Integer;Text,Caption:PChar;Flags:Integer):Integer;stdcall;external'user32.dll'name'MessageBoxA';

　　4.函數重載

functionDivide(X,Y:Real):Real;overload;
begin
　Result:=X/Y;
end
functionDivide(X,Y:Integer):Integer;overload;
begin
　Result:=XdivY;
end;